From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-18.3 required=3.0 tests=BAYES_00,DKIMWL_WL_MED, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,MENTIONS_GIT_HOSTING,SPF_HELO_NONE,SPF_PASS, USER_IN_DEF_DKIM_WL autolearn=unavailable autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id DA88BC433E0 for ; Sat, 16 Jan 2021 00:02:44 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id AB7E723A5E for ; Sat, 16 Jan 2021 00:02:44 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728657AbhAPACo (ORCPT ); Fri, 15 Jan 2021 19:02:44 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:46750 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728604AbhAPACn (ORCPT ); Fri, 15 Jan 2021 19:02:43 -0500 Received: from mail-pj1-x1029.google.com (mail-pj1-x1029.google.com [IPv6:2607:f8b0:4864:20::1029]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 13794C061793 for ; Fri, 15 Jan 2021 16:02:03 -0800 (PST) Received: by mail-pj1-x1029.google.com with SMTP id b5so6152030pjl.0 for ; Fri, 15 Jan 2021 16:02:03 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20161025; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc; bh=FY8VpQNfhIxBmUN0CCall3v72xLkiHt1IqHsb3quwR4=; b=luKEj3UoOFPuOKbYwRLoqFsDstinvsZbmPyy851wXrrnY6L+VRXyETTqdGgw5hGxLP q82oal/qKPyYEtADP0J+9+aBTHtWcStqg7f1d2isGuDnoxu5PU5w2R93MXCZlyflx7l7 2o23TrL3joPsXdxh4adFBgmxw8KI6tA70dzTICQIh6Z6okR/z0pWkGEKOZgja4fDXYdG DyEQN0FCTeWyAWBEferv1Qib1rPFv4dHvg3qKJ+/zKLnUD9LMAW64+23msX/mrMix17s vqPEIc6shaHkKBmGEJoepfmcUzY6UCsQYw68cMqc890Tb5k1Xwy/ExMW6A4K+8uwTgVs azuA== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:cc; bh=FY8VpQNfhIxBmUN0CCall3v72xLkiHt1IqHsb3quwR4=; b=s0//NO63ROZbtzotjXC4MED8QZaBJBww7HtH1oaH0qQ4XPEVqjTJPEwe9OW8lp1f+z CIZ27Vz8hEYtNLP2AMRhbap9PHERMnCjWmXuSw5c23Ibd+lJ9hzLL+uAh247JnFkZa7s iYPmuV2e4UM1phQxrXSjlWVmnXSTPqAFgUZeNWQ8XBcfX0GkttI1xZnbbRbb40x4Dg65 3CAaCdaf7cHi83QPTUejCb6CtE+51FkijCFFeTRPNnOJDtu+V5qtbDY4S2Y9FOI2i648 aaRotv9YbfXSR75Uowu+EaNUa0c+K5XNnpxukLyLscabSbHGqgTTOmqowoq23vJsstXM KZGA== X-Gm-Message-State: AOAM532V5SKYa/W4xOteO/FwH4Lg6kxQ5WGh7Jr19gcIIhT2ZYp2ymOF qckXihT5QbOTwDwCTop2V9soYTkR4rWIdbPSRx4kOg== X-Google-Smtp-Source: ABdhPJzv8hrDv7j8QxBRMT8DbWGNHAjn2SFadQCf6V/1mYcyv79IOw9cqliku5v7+LW/FEZaY2ZCORI+UiGpp+SD2WU= X-Received: by 2002:a17:90a:6ba4:: with SMTP id w33mr13549703pjj.32.1610755322387; Fri, 15 Jan 2021 16:02:02 -0800 (PST) MIME-Version: 1.0 References: <20210112053113.4180271-1-morbo@google.com> <20210113061958.886723-1-morbo@google.com> <20210113205547.GA21653@Ryzen-9-3900X.localdomain> In-Reply-To: From: Nick Desaulniers Date: Fri, 15 Jan 2021 16:01:51 -0800 Message-ID: Subject: Re: [PATCH v4] pgo: add clang's Profile Guided Optimization infrastructure To: Bill Wendling Cc: Jonathan Corbet , Masahiro Yamada , Linux Doc Mailing List , LKML , Linux Kbuild mailing list , clang-built-linux , Andrew Morton , Sami Tolvanen , Nathan Chancellor , Linus Torvalds Content-Type: text/plain; charset="UTF-8" Precedence: bulk List-ID: X-Mailing-List: linux-doc@vger.kernel.org On Wed, Jan 13, 2021 at 8:07 PM Nick Desaulniers wrote: > > On Wed, Jan 13, 2021 at 12:55 PM Nathan Chancellor > wrote: > > > > However, I see an issue with actually using the data: > > > > $ sudo -s > > # mount -t debugfs none /sys/kernel/debug > > # cp -a /sys/kernel/debug/pgo/profraw vmlinux.profraw > > # chown nathan:nathan vmlinux.profraw > > # exit > > $ tc-build/build/llvm/stage1/bin/llvm-profdata merge --output=vmlinux.profdata vmlinux.profraw > > warning: vmlinux.profraw: Invalid instrumentation profile data (bad magic) > > error: No profiles could be merged. > > > > Am I holding it wrong? :) Note, this is virtualized, I do not have any > > "real" x86 hardware that I can afford to test on right now. > > Same. > > I think the magic calculation in this patch may differ from upstream > llvm: https://github.com/llvm/llvm-project/blob/49142991a685bd427d7e877c29c77371dfb7634c/llvm/include/llvm/ProfileData/SampleProf.h#L96-L101 Err...it looks like it was the padding calculation. With that fixed up, we can query the profile data to get insights on the most heavily called functions. Here's what my top 20 are (reset, then watch 10 minutes worth of cat videos on youtube while running `find /` and sleeping at my desk). Anything curious stand out to anyone? $ llvm-profdata show -topn=20 /tmp/vmlinux.profraw Instrumentation level: IR entry_first = 0 Total functions: 48970 Maximum function count: 62070879 Maximum internal block count: 83221158 Top 20 functions with the largest internal block counts: drivers/tty/n_tty.c:n_tty_write, max count = 83221158 rcu_read_unlock_strict, max count = 62070879 _cond_resched, max count = 25486882 rcu_all_qs, max count = 25451477 drivers/cpuidle/poll_state.c:poll_idle, max count = 23618576 _raw_spin_unlock_irqrestore, max count = 18874121 drivers/cpuidle/governors/menu.c:menu_select, max count = 18721624 _raw_spin_lock_irqsave, max count = 18509161 memchr, max count = 15525452 _raw_spin_lock, max count = 15484254 __mod_memcg_state, max count = 14604619 __mod_memcg_lruvec_state, max count = 14602783 fs/ext4/hash.c:str2hashbuf_signed, max count = 14098424 __mod_lruvec_state, max count = 12527154 __mod_node_page_state, max count = 12525172 native_sched_clock, max count = 8904692 sched_clock_cpu, max count = 8895832 sched_clock, max count = 8894627 kernel/entry/common.c:exit_to_user_mode_prepare, max count = 8289031 fpregs_assert_state_consistent, max count = 8287198 -- Thanks, ~Nick Desaulniers